This invention relates to aerosol valves. More specifically, this invention relates to means for assuring that the lower end of the dip tube of such valves remains submerged in liquid to the maximum possible extent.
With present environmental laws restricting the use of chlorofluorocarbons as propellants; aerosol packages are now often driven by compressed gasses such as carbon dioxide or nitrogen. This presents a significant problem: chlorofluorocarbons have recovery power as aerosol propellants. On drop of pressure in the container some of the cfc propellant changes phase to build the pressure back up. In contrast, of course, compressed gases do not recover once the pressure drops.
As a result of this less-than-ideal characteristic of compressed gases as propellants, it is absolutely essential that there be no escape of compressed gases up the dip tube as would occur if the can is tipped during usage and the bottom of the dip tube is exposed to the head space. For this reason it is desirable to provide means to assure that the lower end of the dip tube stay submerged in liquid product to the maximum possible extent.
The prior art has considered keeping the dip tube submerged. Applicants have noted structure in the prior art aimed at accomplishing this objective. It is interesting to note that the aim in the past has been from the point of view of efficiently using the last bit of liquid in the container rather than precluding gas escape. For instance, a U.K. published application of an invention by Fumio Aoki 2,031,526, published Apr. 23, 1980 shows a dip tube having bellows-like configuration with a weight at its lower end so that it operates in any position and so that "the liquid material in the spray vessel can be completely used".
Other examples of flexible dip tubes with weighted ends are:
2,483,661--Neas PA1 4,830,235--Miller PA1 3,130,519--Mauget PA1 5,195,664--Rhea PA1 3,490,656--Taschner PA1 Australian 258,883 PA1 3,547,296--Greenberg PA1 British 2,136,057A PA1 4,273,272--Blanc
The flexibility of such dip tubes has drawn the criticism of the industry in that aerosol assemblies including such tubes have been awkward to handle in production filling lines. Further, such tubes being very flexible have also been susceptible to kinking and closure at the kinks. A still further objection is that the weight in the end of the tubes has made a clunking noise when the container is handled, leading the unsophisticated to believe that something inside is broken. There have been unwarranted complaints.